Evaluating Construction Risks of Ultralarge Diameter Bored Pile in Deep Water Using Combination Weighting with Two-Dimensional Cloud Optimization

The construction of ultralarge diameter bored piles (ULBPs) for cross-sea bridges in deepwater environments is exceptionally complex and faces significant quality assurance challenges. Therefore, accurate risk assessment during construction is essential. This study proposes a construction risk assessment method that combines weighting with two-dimensional cloud optimization. Based on the ULBP construction process, the risk evaluation index system was constructed by identifying six key risk sources, including steel casing deformation, slurry leakage, drill dropping and burying, inclined hole and hole collapse, tremie jamming and blocking, and pouring quality defects. An integrated weighting methodology was implemented to establish optimal index weights, followed by the calculation of two-dimensional cloud model parameters for evaluation indices across risk levels. Risk cloud mapping enabled visualization of assessment outcomes, providing an efficient framework for comprehensive risk evaluation. This risk evaluation system was applied to the Xihoumen Highway and Railway Bridge. Risk factors of steel casing wall thickness, rock-fracturing development, and tremie diameter were identified as high risk. After assessing the outcomes, we devised improvements that successfully ensure the safety and quality of the construction. This demonstrates the risk evaluation system’s reasonableness and feasibility.